Case Study: Wash Won’t Turn Off – Persistent Wash Function / Activation

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Description of Problem: Instead of going into standby mode, the wash remained on with all detergent functions along with hydraulics, rinses, and blowers. Nearly all functions running nonstop as if a customer was approaching.

 

Things to Check: 

1- Are there any incidents that occurred before the problem first began

 

2- Confirm that gate eyes are adjusted properly

 

3- Check that gate sensor (input 12) on the monitor page is illuminated.

 

4- Check photo eye frequencies to confirm that they are ABA or BAB when read from top to bottom. Check that both Drivers and Passengers side Senders/Receiver pairs match frequencies.

> Customer confirmed that drivers side was set to ABA, however the passengers side sensors (emitters) had no illuminated lights whatsoever.

 

Analysis: With the passengers side not illuminated the most likely case for the persistent wash operation is in the power supplied to the passenger side gate sensors.

 

Conclusion: Customer checked and confirmed that the wiring that feeds the passenger side gate sensors was corroded. Once the wiring was replaced normal wash function was restored. The passenger side houses the sensor emitter which sends out a beam of light to the receiver (drivers side sensor). When the receiver failed to pick up the light it continually provided a 24vdc signal to the controller, indicating that the eye was blocked and to begin the wash process, resulting in the persistent wash operation.

 

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